Submitted by Tom Laird WC9M * 23 Jan 98

The original TR-6 receiver uses TIS-88 transistors in the RF amplifier section.

Since the original design, better FET transistors have been developed, with higher gain and lower noise figures.

DRAKE has been updating the TIS-88 with J-310 FET's, but an even better FET is the U-310.

Replacing these two RF amp FET's is not hard if you are handy with a soldering pencil. You will need two hemostats to protect the FET from damaging heat.

Remove the bottom cover (6 screws) and turn it upside down with the knobs facing you.

Locate the "REC GAIN" knob at the lower right corner. Directly to the rear of the double pots is a dual compartment which contains a slug tuned coil (L-10 on schematic).

Directly to the front of that coil are two inverted transistors with the leads easily accessible. Remove the original transistors and install the U-310's in their place.

See drawing #1 for transistor location, drawing #2 for enlarged detail and drawing #3 for U-310 detail. Note that the U-310 has a metal case, do not let it touch chassis ground.

Two heat sinks must be used when soldering the legs common to both FET's.

This mod is at least ten years old, so better components may be available. The original U-310's were purchased from RF Parts, but they may not stock it now. YMMV (Your Mileage May Vary).

Tom Laird WC9M
Moline, IL.
Note: original modification by L.J.Hemmis K3VLQ

Return to Drakelist Comments for K3HRN

Layout and Design Copyright © 2000 by K3HRN
All Rights Reserved